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sunrpc: make xprt->swapper an atomic_t 

Split xs_swapper into enable/disable functions and eliminate the
"enable" flag.

Currently, it's racy if you have multiple swapon/swapoff operations
running in parallel over the same xprt. Also fix it so that we only
set it to a memalloc socket on a 0->1 transition and only clear it
on a 1->0 transition.

Cc: Mel Gorman <mgorman@suse.de>
Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
Reviewed-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
This commit is contained in:
Jeff Layton 2015-06-03 16:14:26 -04:00 committed by Trond Myklebust
parent 3c87ef6efb
commit 8e2281330f
3 changed files with 30 additions and 17 deletions
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5
include/linux/sunrpc/xprt.h
View File

@ -180,7 +180,7 @@ struct rpc_xprt {
atomic_t num_reqs; /* total slots */
unsigned long state; /* transport state */
unsigned char resvport : 1; /* use a reserved port */
unsigned int swapper; /* we're swapping over this
atomic_t swapper; /* we're swapping over this
transport */
unsigned int bind_index; /* bind function index */
@ -346,7 +346,8 @@ void xprt_release_rqst_cong(struct rpc_task *task);
void xprt_disconnect_done(struct rpc_xprt *xprt);
void xprt_force_disconnect(struct rpc_xprt *xprt);
void xprt_conditional_disconnect(struct rpc_xprt *xprt, unsigned int cookie);
int xs_swapper(struct rpc_xprt *xprt, int enable);
int xs_swapper_enable(struct rpc_xprt *xprt);
void xs_swapper_disable(struct rpc_xprt *xprt);
bool xprt_lock_connect(struct rpc_xprt *, struct rpc_task *, void *);
void xprt_unlock_connect(struct rpc_xprt *, void *);

4
net/sunrpc/clnt.c
View File

@ -2495,7 +2495,7 @@ rpc_clnt_swap_activate(struct rpc_clnt *clnt)
goto retry;
}
ret = xs_swapper(xprt, 1);
ret = xs_swapper_enable(xprt);
xprt_put(xprt);
}
return ret;
@ -2522,7 +2522,7 @@ rpc_clnt_swap_deactivate(struct rpc_clnt *clnt)
goto retry;
}
xs_swapper(xprt, 0);
xs_swapper_disable(xprt);
xprt_put(xprt);
}
}

38
net/sunrpc/xprtsock.c
View File

@ -1961,31 +1961,43 @@ static void xs_set_memalloc(struct rpc_xprt *xprt)
struct sock_xprt *transport = container_of(xprt, struct sock_xprt,
xprt);
if (xprt->swapper)
if (atomic_read(&xprt->swapper))
sk_set_memalloc(transport->inet);
}
/**
* xs_swapper - Tag this transport as being used for swap.
* xs_swapper_enable - Tag this transport as being used for swap.
* @xprt: transport to tag
* @enable: enable/disable
*
* Take a reference to this transport on behalf of the rpc_clnt, and
* optionally mark it for swapping if it wasn't already.
*/
int xs_swapper(struct rpc_xprt *xprt, int enable)
int
xs_swapper_enable(struct rpc_xprt *xprt)
{
struct sock_xprt *transport = container_of(xprt, struct sock_xprt,
xprt);
int err = 0;
if (enable) {
xprt->swapper++;
xs_set_memalloc(xprt);
} else if (xprt->swapper) {
xprt->swapper--;
if (atomic_inc_return(&xprt->swapper) == 1)
sk_set_memalloc(transport->inet);
return 0;
}
/**
* xs_swapper_disable - Untag this transport as being used for swap.
* @xprt: transport to tag
*
* Drop a "swapper" reference to this xprt on behalf of the rpc_clnt. If the
* swapper refcount goes to 0, untag the socket as a memalloc socket.
*/
void
xs_swapper_disable(struct rpc_xprt *xprt)
{
struct sock_xprt *transport = container_of(xprt, struct sock_xprt,
xprt);
if (atomic_dec_and_test(&xprt->swapper))
sk_clear_memalloc(transport->inet);
}
return err;
}
#else
static void xs_set_memalloc(struct rpc_xprt *xprt)